Water

Question 1

Shape and structure of water molecule

Answer 1

Shaped like wide V
Two hydrogen atoms joined to an oxygen atoms by single covalent bond

Question 2

Water molecule’s polarity

Answer 2

water is a polar molecule because oxygen is more electronegative than hydrogen so the shared pair of electrons pair spend more time near oxygen forming polar covalent bond

Question 3

Overall charge of water molecule

Answer 3

Oxygen contains two regions of partial negative charge and hydrogen has a region of partial positive charge

Question 4

Which type of bond is held two water molecules together?

Answer 4

Hydrogen bond

Question 5

Six properties of water

Answer 5

1.Polarity
2.Excellent solvent
3.High heat capacity
4.Cohesion(high surface tension)
5.Adhesion
6.Low density when frozen

Question 6

How water can be excellent solvent?

Answer 6

As water molecule is polar molecule,it can dissolve poler molecules and ions due to its ability to form ion-dipole and dipole-dipole interactions

Question 7

What is cohesion?

Answer 7

Attraction between water molecules

Question 8

What is adhesion?

Answer 8

Attraction between water molecules and other substances

Question 9

What is surface tension?

Answer 9

A measure of how difficult it is to stretch or break the surface of a liquid

Question 10

Why water molecules have high surface tension?

Answer 10

At the interface between water and air,water molecules are hydrogen-bonded to one another to water molecules below but not to the above air

Question 11

What is kinetic energy?

Answer 11

The energy of motion

The faster a molecule moves,the greater its kinetic energy

Question 12

What is thermal energy?

Answer 12

The kinetic energy associated with random movements of atoms and molecules

Question 13

What is difference between thermal energy and temperature?

Answer 13

Thermal energy of a body of matter is the total kinetic energy that depends on matter’s volume

Temperature is the average kinetic energy of molecules in body without the volume of the body

Question 14

What will happen when two objects with the different temperature are brought together?

Answer 14

Thermal energy passes from warmer objects to cooler object until the two are at the same temperature

Question 15

What is heat?

Answer 15

Thermal energy in transfer from one body of matter to another

Question 16

Units of heat

Answer 16

Calorie(cal)-amount of heat it takes to rise the temperature of 1g of water by 1 C
Kilocalorie(kcal)-1000cal-amount of heat required to raise the temperature of 1kg of water by 1•C
Joule

Question 17

Specific heat

Answer 17

The amount of heat that must be absorbed or lost for 1g of substance to change its temperature by 1•C

A measure of how well a substance resists changing its temperature when it absorbs or releases heat

Question 18

Water’s specific heat

Answer 18

1cal/(g •C) i.e.1 cal of heat is required for 1g of water to change its temperature by 1•C

water resists changing its temperature when it absorbs or releases heat

Question 19

Water’s high specific energy compared to ethanol

Answer 19

Water-1cal/g•C
Ethanol-0.6cal/g•C

Question 20

What is heat of vaporization?

Answer 20

The quantity of heat of a liquid must absorb for 1 g of liquid to be converted from liquid to gaseous state

Question 21

Do water have high heat vaporization?

Answer 21

Yes

Question 22

Density of ice vs liquid water

Answer 22

Ice has lower density than liquid water because of crystalline lattice structure of ice

Question 23

What is water density at 4•C and above?

Answer 23

At 4•C,like other liquids water expands as it warms and water contracts as it cools

Question 24

Water density at below 4•C-0•C

Answer 24

Water begins to freeze because more and more of its molecules are moving too slowly

At 0•C,the molecules is locked into crystalline lattice structure

Question 25

what is solvent?

Answer 25

Dissolving agent of a solution

Question 26

What is solute?

Answer 26

The substance that is dissolved in solution

Question 27

What is solution?

Answer 27

A liquid that is completely homogeneous mixture of two or more substances

Question 28

What is aqueous solution?

Answer 28

The solute is dissolved in water water is the solvent in aqueous solution

Question 29

Which solutes can water dissolve?

Answer 29

Ionic molecules and polar molecules

Question 30

Hydrophilic molecules

Answer 30

Molecules that have affinity for water (ionic and polar molecules) water-loving molecules

Question 31

All hydrophilic molecules are dissolved in water.True or false?

Answer 31

False,substances can be hydrophilic without actually dissolving Eg.cotton

Question 32

Hydrophobic molecules

Answer 32

Substances that do not have an affinity for water (nonionic and non-polar molecules) water-hating molecules

Question 33

What is molarity?

Answer 33

Molarity is the unit of concentration The number of moles of solute per liter of solution

Question 34

What is mole?

Answer 34

A mole is a certain number of molecules of a substance.

Question 35

What is molecular mass?

Answer 35

The mass of a mole of substance in grams

Question 36

Water dissociation

Answer 36

When two water molecules are connected by a hydrogen bond ,hydrogen ions(H+) is transferred to one molecule to another forming Hydronium ions(H3O+) and the molecule that lost hydrogen ion becomes hydroxide ion(OH-) It is the reversible reaction and reaches at a state of equilibrium

Question 37

What is the concentration of H+ and OH- in pure water?

Answer 37

same concentrations

Question 38

What is acid?

Answer 38

A substance that increases the hydrogen ion concentration of a solution HCl——->H+ +Cl-

Question 39

What is base?

Answer 39

a substance that reduces the concentration of H+ ion Some bases reduce H+ conc directly by accepting hydrogen ions and other bases reduce reduce H+conc indirectly by dissociating to form OH- ions

Question 40

What is acidic solution?

Answer 40

Solution with higher concentration of H+ ions than OH- ions acidic solution have pH value of less than 7

Question 41

What is basic solution?

Answer 41

A solution with higher concentration of OH- ions than H+ions basic solutions have pH value of greater than 7

Question 42

How strong acid and strong base dissociate in water?

Answer 42

Completely dissociate Eg.HCl and NaOH

Question 43

What is weak acid and weak base?

Answer 43

The substance that dissociates partially in water

Question 44

In which temperature,the product of [H+][OH-] concentration is constant?

Answer 44

25 degree Celcius

Question 45

In 25 degree Celcius,the product of [H+][OH-] concentration is constant.What is tha value of this constant?

Answer 45

[H+][OH-]=10 *-14 So [H+]=10* -7 and [OH-]=10* -7

Question 46

When enough acid is added to the solution to increase [H+] to 10*-5M ,what is [OH-] value?

Answer 46

10* -9 M

Question 47

When enough base is added to the solution to increase [OH-] to 10*-4M ,what is [H+] value?

Answer 47

10* -10 M

Question 48

pH and [H+] relation

Answer 48

pH=-log[H+] pH decreases as H+ concentration increases

Question 49

pH 1 example

Answer 49

Battery acid

Question 50

pH 2 example

Answer 50

Gastric juice(HCl in stomach) Lemon juice

Question 51

pH 3 example

Answer 51

Vinegar Wine Cola

Question 52

pH 4 and 5 example

Answer 52

Tomato juice Beer Black coffee

Question 53

pH 5.5 example

Answer 53

rain water

Question 54

pH 6 example

Answer 54

Urine

Question 55

pH 7 example

Answer 55

Saliva Pure Water Human blood Tears

Question 56

pH 8 example

Answer 56

seawater inside small intestine

Question 57

pH 10.5 example

Answer 57

Milk of magnesia

Question 58

pH 11.5 example

Answer 58

Household ammonia

Question 59

pH 13 example

Answer 59

Household bleach

Question 60

pH 13-14 example

Answer 60

Oven cleaner

Question 61

pH value of blood

Answer 61

7.4

Question 62

How strong acid effect on pH value of pure water?

Answer 62

if 0.01 mol of strong acid is added to 1L of pure water,pH drops from 7.0 to 2.0

Question 63

If 0.01mol of strong acid is added to 1L of blood,how the pH value change?

Answer 63

pH value decrease only 7.4 to 7.3

Question 64

Why does tha addition of strong acid of acid have so much less effect on pH of blood than it does on pH of pure water?

Answer 64

The presence of buffers in biological fluids to maintain constant pH despite the addition of acid or bases

Question 65

What is buffer?

Answer 65

a substance that minimizes changes in the concentration of H+ and OH- in a solution Most buffer solutions are weak acid and its corresponding base,which combine reversibly with H+ ions Eg.Carbonic acid H2CO3 Acetic acid CH3COOH

Question 66

How carbonic acid dissociate as buffer solution?

Answer 66

Carbonic acid dissociates into a bicarbonate ions(HCO3-) and hydrogen ions(H+) The reaction is reversible and is in equilibrium state

Question 67

What will happen if the H+ concentration in blood begins to fall?

Answer 67

when [H+] fall in blood, pH of blood will rises So more carbonic acid dissociates and replenishes H+ ions

Question 68

What will happen if the H+ concentration in blood begins to rise?

Answer 68

when [H+] rise tha pH of the blood drops So HCO3- and H+ ions will react to form more carbonic acid(H2CO3)

Question 69

Is that correct most buffers are acid-base pairs?

Answer 69

Yes